Six-port technology and applications

A short review of the six-port theory for usual applications in down-conversion, direct modulation, and direction finding techniques is presented in this paper. Implementations of the circuit in various mature fabrication technologies, covering millimeter wave frequencies up to 94 GHz, are exemplified. Circuit characterisation method using a precision network analyser and on-wafer measurements are described in details. Measurement results of various passive circuits, from a novel power-divider to a 60 GHz six-port circuit, are discussed, validating very good S-parameter and q_i point performances. System measurements, using a six-port front-end imbedded in 77 GHz heterodyne FMCW radar, conclude the paper.